Gas producer



W. B. CHAPMAN.

GAS PRODUCER.

APPLICATION FILED IAN-18, 9l6- Patented Apr. 18, 1922.

5 SHEETS-SHEET l.

5 num/Lto@ W. B. CHAPMAN.

GAS PRODUCER.

APPLICATION FILED JAN. I8, I9I6.

Patented Apr. 18, 1922.

5 SHEETS-SHEET 2.

Z/ ZIA/ 1 L j *Li Swva-nfoz @513 @man W. B. CHAPMAN.

GAS PRODUCER.

APPLICATION FILED JAN. 18, 1916.

1,412,921. Patented Apr. 18, 1922.

5 SHEETS-SHEET 3.

3 wko@ 1% @M 59 a @Hom/w13 W. B. CHAPMAN.

GAS PRODUCER.

APPLICATION FILED IAN. I8, I9I6.

5 SHEETS*SHEET 4.

11,412,921., l Patented Apr. 18, 1922.

Z4 mi W. B. CHAPMAN.

GAS PRODUCER.

APPLICATION FILED JAN-18.19IE.

1,412,921. Patented; Apr. 18, 1922.

Y. SHEETS-SHEETS.

UNITED STATES PATENT OFFICE. f

WILLIAM B. CHAPMAN, OF MOUNT VERNON, OHIO, ASSIGNOR '.lO CHAPMAN ENGI- NEERING COMPANY, OF MOUNT VERNON, OHIO, A CORPORATION OF OHIO.

GAS PRODUCER.

Specification of Letters Patent.

Patented Apr. 18d, 1922.

Application led January 18, 1916. Serial No. 72,705.

' and exact terms as will enable any person skilled in the art to which it pertains to make and use the same.

The object of my invention is to secure a mechanically operated producer having the least possible number of moving parts and those as lightas may be consistent with their functions.

In making producer gas it is desirable to perform the following operations, not only continuously and automatically, but in a definite synchronism or harmony with each other, to wit;-

(a.) Feeding the fuel.

(b.) Uniformly spreading the fuel.

(c.) Agitation of the surface or top strata of the fuel, and l (d.) Removal of the ash.

These operations should go on continuously or periodically at fixed and definite rates which are in perfect unison or synchronism with eac-h other, in order that'the gas making process be scientifically regulated; and these ends should be accomplished without moving any heavy or ponderous parts of the producer, such as the walls of the producer body or the ash pan or even the top of the producer body.

To this end my invention involvesvarious features and combinations, including (a.) A coal supply or charging means adjustable so that the fuel is fed in unison with the rate of gasification:

(band c.) An agitator operating in the top strata. of the fuel or on its top surface and automatically adjustable vertically to accommodate it to the varying level of the fuel, the agitator serving to spread the green coal out on the fire and to keep such fuel compact and uniform; and i (d.) An ash removal `means operating continuously to remove the ash at the base of the producer also in unison with the rate of fuel gasification which is essentially the same as the rate of ash formation.

The parts above enumerated preferably are the only moving` parts and by their organization and operation as above indicated an automatically operative or so called mechanical gas producer is provided whose operation is perfectly suited to the natural laws of 'the gasification of coal, the elements working together synchronously each at the rate required for the proper gasification of the coal and removal of the ashes and forming a` perfectly balanced combination adapted to the process of automatically transforming coal into what is known inthe arts as producer gas.

Reference is now had to the accompanying drawings which illustrate as an example, the preferred form of my invention and in which- Figure 1 is a vertical section showing the machine generally; i

Figure la is a detail plan of the agitator arms;

Figure 2 is an enlarged sectional elevation of the agitator devices;

Figure 31- b is an enlarged vertical section of the agitator and its immediate/parts;

Figure 4 is a cross-sectional plan at the line 4-40f the Figure 3a'-3;

Figure 5 is a cross-section on the line 5-5 of Figure 3b;

Figure 6 is an enlarged cross-section on the line 6-6 of Figure 3b;

Figure 7 is a section of the charger on the line 7-7 of Figure '8;

Figure 8 is a section on the line 8 8 of Figure 7; i

Figure 9 is aI detail of the charger fingers.

Referring first'to Figure 1 the producer has stationary side walls 10 sustained through stationary feet 11 on the bed or l foundation 12. The lower edge of the stationary producer wall dips into a water. sealed ash pit 14 in the base or foundation 12. The top 15 of the producer is.

grate-tuyere 16 also stationary as is the through which the blast current entersthe so that it may run in a circular path around the bottom part of the producer. The ring or annulus 19 carrying the ash plow 18 is.,`

driven by worm gear 21 operated from ,a swinging arm 22 and awl and ratchet delvice23 with a 'connection 22 from the arm to source of power. rlihe plow is thereby "given a very slow motion (the speed of which may be regulated and adjusted easily) through the ash pit and, the plow being set on an angle, causes the movement yof the 'ash upward in the pit which would linally result in the ash crowding out on l the floor beyond the pit. rllhe ash may be removed from the outer part ofthe pit as desired either by manually shoveling or byl some form of automatic device such for example, as that shown in my prior Patent No.

1,165,569 dated December 28 1915.

'llhe agitator '24 lies horizontally in the producer and presses down on the surface of the coal or on the top strata thereof by its own weight and any desired additionalA downward pressure, for example, the weight box 25 attached to the central stem -26 of the agitator. rllhe agitator is freely movable-vertically to accommodate itself to the level of the coal and the condition of the re inthe producer. It yrises and falls automatically according to the' combined eii'ect of the yheight of the fuel and its density.

. Whenever the agitator in cutting or plow- .sol

ing through the topI of the coal meets with an abnormal resistance the controlling and drivingl devices of the agitator exert a corresponding lifting power on the stem 26 and lift the agitator to or toward the top of the coal. When the above mentioned resistance is removed the agitator automatically tends to return to its iirst position and is always in vbalance with the various forces `.acting upon it. e

' The agitator is simultaneously rotated or `turned continuously on or in the coal and thereby serves to level or spread and uniformly compact the'same. As will hereinafter appear this operation is varied and controlled by the varying torsional. strain or twisting moment exerted on the agitator due to its rotation on or in thev coal. 4As will also appear hereinafter. the mechanism for l .driving and controlling the agitator, like the ash plowconnection 22a,takes its power from and is controlled by the prime mover or common source of power to the producer.

The producer is charged periodically accordin to the progresss of the gas making operatlon through a chute 29 which is provided with a quick opening and quick closing lgate 28 having an automatic operating mechanism driven by a link beltA or other connection 29L with the source of power and driven thereby in harmony with the other operations hereinbefore described. The chute 29 delivers v`into a throat which takes the coal into the top ofthe producer' at the center thereof and 30 represents a combined bearing for `the I agitator stem 26 and spreader fo-r the coal which causes the coal to fall in an Kannularlpile around the center of the producer somewhaty like that in` Ldicated by the broken lines 31 in Figure 1 which pile is immediately leveled out and disposed uniformly with `the .previously charged contents of the producerby the before described operation of the agitator scription of the outlines ofl my improved gas producer; after the ire'has been started in the usual way and the operation becomesV normal the blast current keeps the gas making process going on at the predetermined desired Vrate and the agitator operatesthe coal at which point the coal is generally described as green or unburned and is first taking the heat of the gas making operation with the result that the coal tends to ag# glomerate with cracks or hot spots intervening. rlhe 'steady progress of the -agitator on Vand through the coal at this point distributes the coal evenly and compacts the same at the loose or open places so that uniform conditions are obtained and the formation of air passages through the fire and the uneven or unequal movement of the blast current are prevented. This keeps the fire at an equal degree .of intensity transversely throughout the producer. rlhe ashes form continuously according to the rate of gasification and the action of the agitator tendsto keep the lire Compact and pressing down on the ashes. The ash plow, operating continuously, is regulated to withdraw the ashes at Va rate just equal to the rate of {their accumulation. The charging device meanwhile opens its gate atintervals, which depend upon the rate of coalv consumption in the producer, and deposits measured quantities of fresh coal on top of the fire which is immediately leveled out and compacted by the agitator in the fashion before described. Myexperiments` have demonstrated that by this coordination of parts I am enabled to secure a gas producer in which the fewest possible movlng parts are necessary -and the great y work and expense of rotating the body of the producer itself is avoided and yet, at the same time, l secure a perfectlyvautomatic machine which carries out the necessary mechanical operations, not in an uncontrolled way, but flexibly and controllably in a way which may be directly suited through proper 1,451 aaai adjustment of the physical conditions of the gas making process which natural conditions engineers are not able to change or adjust.

l provide for the peculiar'loating, coalsurface, agitator, preferably as shown in Figure 2 to Figure 6, with a cable system which is at the vsame time the supporting means and the driving gear for imparting rotary motion to the agitator. 'The agitator arm or arms 24 are tubular and joined'to the stem 26 which is also tubular. This is to allow water-cooling the arms 24, the water being introduced under pressure through a tube 33 which passes through the tubular stem 26 and has branches 34 discharging the water in the outer ends of the arms 24, the water returning through the stem 26 outside of the pipe 33.

The stem 26 and its tube 33 (see Figures 2-6) extend through the water cooled guide which projects through the top 15 of the producer and is fastened thereto. rllhis guide 50 has inner and outer walls forming a chamber in which water collects and is discharged through the opening 51 onto the producer top 15. ln the chamber formed by the guide 50 a tubular skirt 52 projects loosely and carries a bucket 25 at its top outside of the producer which is adapted to be loaded with suitable weights. rllhis skirt 52 incloses the stem 26 and the stemy also is fastened to the bucket 25 so that the weight ot the bucket is transmitted to the stem and agitator arms 24 pressing the arms down on the coal with the desired force which is regulated by the weights in the bucket 125. rlhrough the bucket 25 a tube 53 extends forming a continuation of the stem 26 and this is connected by suitable rotary joint 54 with a shackle 55 through which the agitator is lifted together with the parts attached thereto. An extension tube 56 communicates with the tube 33 to supplyv it with water. The tuber56 extends through the tube 53 Aand is inV connection with the supply through a hose or the like 57.

The skirt 52 has one or more keys or splines 58 (see Fig. '4) thereon which extend throughout its upper portion down to a point near its lower end as shown in Fig. 3b, and surrounding the skirt is the hub 59 of a sheave 60 which hub has a number of in'- ternal shoulders or lugs adapted to engage the spline 58 so as to cause the sheave and skirt 52 to rotate together, but if the skirt be raised to its extreme upper position`the spline 58 will disengage from the ribs of the sheave hub and then the sheave will be free to turn idly around the lower part of the skirt until the skirt is again lowered and reengages its spline ywith the hub of the sheave and the two parts then again operate together. ln Fig. 1, the skirt is omitted, the spline being on the stem 26.

The sheave 60 rests loosely on the top of the guide 50 and carrying an idler sheave 37 also with a plurality of grooves in its periphery taking from the periphery of the sheave 6() the various turns of the said driving cable. 38 are single grooved sheaves mounted on the arm 36 and past which the runs of the driving cable extend upward respectively to sheaves 39 and 40 on a suitable overhead support (see Fig. 2). llrom the sheave 39 the cable runs down to a sheave 41 fastened to the shackle 55. From the sheave 41 the cable runs up to a sheave 42 on the overhead support and thence over to a driving or prime mover sheave 43. 44is an idler sheave, between which and the sheave 43, a number of turns of the driving cable pass so as to make the necessary trictional contact between the cable and the driving sheave 43; and from thence the cable runs down around a sheave 45 on a takeup or tension weight 46 and back to thc before described sheave 40.

New, having in view that the problem is to cause the agitator arms 24 to operate atV or in the top stratum of the coal and to simultaneously turn to level and compact` the same, it will be observed, that the agitator and its connected parts are, by means of ithis peculiar cable arrangement, suspended in their operative position and pressed down by thelr own weight, and that of the contents of the bucket 25, into or on the coal with the predetermined degree of pressure. At the same time this group of parts is sustained or supported by the cable and the cable kept taut by the counterweight 46 and, further still, the cable, being driven from the driving pulley, 43, continuously as the arrows in Figure 2 denote, will impart a steady rotation to the sheave b() and by the before described arrangement of this sheave the agitator is rotated. Therefore the agitator' raises and falls to accommodate itself tothe changing level of the coal or the density of the tire bed and simultaneously turns on or in the same according to thedegree of downward pressure that is applied t0 the agitator.

Should the coal cover the agitator excessively, or if any other excessive resistance be offered to the rotating motion of the agitator (for example, a big lump of coal in its path) the eiect of the cable drive and its counterweight or tension 46 will be i Ato pull upward on the sheave 41 and lift the sheave with its connected parts (which includes the agitator) pulling the agitator upward. If this effect becomes excessive (lue to too much fuel or ash in theproducer the upward motion of the agitator and its connected parts, which includes the skirt 52, results in lifting the spline 58 out of engagement with the hub 59 and then the sheave turns idly on the lower part of the skirt 52 and the rotation of the agitator 1n the coal ceases. When this happens the excessive tension on the cable is relaxed and the weight bucket 25 and its connected parts including the agitator tend to descend, and as soon as the fire bed lowers to .within its operating limit the splinevre-engages the hub of the sheave 60`and the agitator is again rotated. l

The disengagement of the spline is a safety device and does not o erate except in case a mistake has been ma e and -the pro ducer charged too full. This mechanism, it will benoted, serves the purpose of maintaining the agitator automatically at its proper position on or in the top stratum of' the coal and insuring the rotation of the agitator when it is active. Should an excessive amount of coal be charged in on the top of the agitator, raising the level of the fuel beyond its intended limit, the effect on the apparatusis to increase the tension on the pulling run of the cable thereby cause the agitator to screw or twist itself out of the coal/y on a spiral courseafter which the agitator drops back, the spline runs into the sheave and the agitator is again rotated in its normal or active position.

The whole mechanism is automatic and is of the simplest and most durable character, and the agitator has a balanced action between the forces that control it. Further,

`it involves very few moving mechanical parts and none of these are delicate or in any manner exposed to undue heat or Wear ordinarily present in gas producer practice.

The means for charging the fresh or green coal into the producer operate in a fixed relation, as totime, with the other parts and are shown in detail in Figur 7 to 9. In

Figure 7 a slight modification in the arrangement at the top of the producer is indicated, the same consisting in a combined agitator-stem guide and coal spreader formed of alhollow metal casting'65 located centrally under the top of the producer and supported by hollow water circulating arms i 66 depending from and communicating with the water pan 67 in or on the top of the producer. Extending v'from this owater pan is a column 68 forming the coal entrance chute and havinga laterally disposed hopper-like portion 69- terminating in a crescent shaped distributer lip 70 which causes the coal, sliding in laterally from the hopper 69, to be deposited centrally upon the cone yshaped spreader 65, and, falling from the latter, to Ilie centrally on the fuel bed as indicatedby the before described broken lines in Figure 1. My invention is not limited to the manner in which the stem 26 of chain and other devices.

tating the agitator is indicated by broken lines in Figure 7.

Into the top of the hopper-like extension 69 the coal chute 72 leads, -as here shown, in a diagonal direction, its lower end entering the hopper 69 and formed on an arc to accommodate the arc-shaped gate 72"al which opens and closes the chute admitting measured quantities of coal at stated intervals which intervals should correspond with the rate of gasification and with the operation ofthe other parts of the producer. The gate, as shown best in Figure 8, is hung from two trunnions 73 and 74 by means of arms 75 at the sides of the chute 72h but within the hopper 69. These trunnions are mounted in a suitable box on the top of the hopper 69. A

The trunnion 74 has a weighted arm 76 keyed to it and outside of this arm' a weighted arm 77 is mounted loosely on the trunnion 74. The arm, 77 has a toe 78 fastened to it and the same is adapted to coact with a p-inV 79 (see Fig. 9) adjustable by suitable sc1fe\vs\80 on an arm 81 -keyed to a constantly rotating shaft 82 which is driven.

in time with the other parts of the producer from the prime moverlor jack shaft before described. This driving of the shaft 82 may be accomplished by a sprocket wheel 83 and the usual complementar' Said sprocket 83 rotates slowly in the direction of the arrow indicated in Figure 7 and the arm 81 turning with the shaft of the sprocket periodically strikes the toe 78 (through the pin 79) and lifts the weighted arm 77 from the lower position shown by broken lines in Figure 7 to the upper position, also shown by broken lines in Figure 7. (The arms 77 and 76 are shown by broken lines in Figure 7 because the line of Seetion indicated at 7-7, Figure 8, will not allow of showing these parts by full lines). The weight 76 serves to close the gate 72B, (this closed position being shown by the lower dotted position of the weight in Figure 7) and the weighted arm 77 is adapted to fall behind the arm 76 and .to overtake and strike the same asit approaches the lower position thereby assisting theaction of the arm 76.

The rotating shaft82 extends across the device to the side opposite the weighted arm 76 and 77 and carries at its said extended end a mutilated spur `gear 84 adapted to mesh withothe similar gear (thoughl of a broader face) 85 which is loose on an exten' sion 83a of theltrunnion 73; and this gear 85 and the trunnion 7 3 have coacting teeth 88 which when engaged fasten the gear 85 to the trunnion and when disengaged allow the gear to rotate independently of the trunnion. This engaging and disengaging action is allowed by a spring 87 on t-he exten- The purpose of the above described mechf anism is to open and close the gate 72L at stated intervals and also to operate it with a certain abruptness or jolting which prevents clogging or arching of the coal in the chute 72. lhe gate is primarily closed by the weight 76 but, as has been noted, this weight on its downward orclosing movement is overtaken by the weight 77 which strikes the weight 78 and assists the closing movement at the same time bringing the gate closed with a considerable jar. rlhe arm 8l rotating with the shaft 82 strikes the finger 78 when the same is raised as in the upper position shown in figure 7 and this lifts the arm 77 back to its raised position ready for a second operation. The mutilated gears 84 and 85 'lift the arm 90 to the position shown by full lines in Figure 7 and when these gears run out of mesh the arm swings rightward and downward; the teeth 86 are then in lock with each other and the swinging motion of the arm 90 is transmitted to the gate 72a opening the same. At this time the finger 89 strikes the inclined cam 88 and arm 90 is moved outward so that the teeth 86 pass each other and are ready to re-engage when the operation is repeated. 'Simultaneously the roller 79 and arm 81 acting on the finger 78 will have lifted the weight 77 and when the roller runs off the finger the weight 77 drops back leftward (referring to Figure 7) and the weight 77 being heavierthamthe weight 76 overtakes the weight 76 with a sharp blow and the combined effort of the J two weights brings thel gate 72a" (which meanwhile has been opened) shut with some violence` It is this violent or jolting. action which shakes down the cal in the chute and prevents it from arching or ologgin therein.

lrfence it will be seen that the continuously rotating shaft 82 brings about this jerky yet regular action of the gate and periodically admits measured quantities of coal into the producer, the ,weight 90 falling rightward to open the gate and then striking its finger 89 on the cam 88 sothat the teeth 86 may move past each other ready for a repetition of the operation and the weight 77 being lifted by the roller 79 and finger 78 and falling back leftward to assist in bringing the gate 72a shut. rl`his peculiar operation goes on steadily resulting in the automatic charging of the producer at the definite intervals provided for.

In the operation of the producer, the amount of fuel fed, and ash removed, will be adjusted to accord with the rate of gasification desired. l/Vith most fuels, when the producer is to be run at only a fraction of its capacity, it is necessary to reduce the thickness of the fire bed correspondingly, else the slow rate of consumption of fuel will render the top stratum of the lire bed so green and sticky or caked, that forced draft does not pass effectively or evenly through the same. rll`he type of agitator disclosed readily adjusts itself to any height of fire bed, and thus acts in conjunction with thefuel feeding and ash removing means to permit the continuous generation of gas at the desired rate.

l claiml. A gas producer having means for maintaining a stationary body of fuel, an agitating means working continuously at the top stratum of the fuel to distribute the same around the fuel bed and produce substantially uniform conditions of combustion throughout the fuel bed, mechanism to regulate the height of this agitating means to correspond to the thickness of the fuel bed, means for removing ash'from the lower portion of the fuel bed, and means for feeding fuel to the producer in synchronism with the removal of the ash, whereby fuel may be automatically fed and operated on by the agitating means at the proper rate under different rates of gasification and with dlfferent thicknesses of fuel bed, and the ash automatically removed from the lower portion of the fuel bed at a rate commensurate with the aforesaid operations of feed and gasification.

2. A gas producer having stationary walls and bottom supporting parts 'adapted to maintain a stationary body of fuel, a rotary agitating means working continuously at the top stratum of the fuel to-distribute thesame around the fuel bed and produce substantially uniform conditions of combustion throughout the fuel bed, mechanism to regulate the height of the agitating means to correspond to the thickness of the fuel bed, a water seal below the fuel bed of the producer, an ash-removal means adapted to remove the rash through said water seal and clear of the producer walls, and means for feeding lfuel to the producer in synchronism with. the removal of the ash, whereby fuel may be automatically fed and operated on by the oa itating means at the proper rate under di erent rates of gasification and with different thicknesses of fuel .bed, and

ica`

the ash automatically removed from the lower portion of the fuel bed at a rate commensurate with the aforesaid operations of feed and gasification.

3. A gas producer having means for maintaining a body of fuel, means for feeding fuel to the producer at a rate adjustable to conform to the desired rate of gasification, agitatingmeans Working continuously at the top stratum of the fuel to distribute the same around the fuel bed and produce substantially uniform conditions of combustion throughout the fuel bed, means for causing arelative horizontal travel between the fuel body and the agitating means,

mechanism to regulate the height of the agitating means to correspond to varying thicknesses of the fuel bed, and adjustable means for removing ash from the lower portion of the fuel bed at arate commensurate with the aforesaid operations of fuel feed and gasification.

4. A gas producer' having means to maintain a stationary fuel bed, means continuously to agitate the top stratum or surface thereof and means continuously to removel the ash clear of the producer walls, devices for driving both of said means in a definite relation to each other and to the thickness of fire bed employed for the desired rate of gasification of the coal, and mechanism to automatically regulate the height of the agitator to correspond to the thickness of the fire bed employed for the rate of gasification desired and quality of fuel.

5. In a combination with means for sup- =portin a fuel bed, an agitator having an upwar ly extending portion, means for causing a relative rotation between said bed and agitator, .and means governed by the horizontal twisting moment produced by the fuel upon the agitator and transmitted to said upwardly extending portion, for adjusting the elevation of the agitator.

6.' 'In combination with means for support,- porting a fuel bed, an agitator, means for causing relative rotation between said bed and said agitator, and means governed by the horizontal twisting moment produced by the fuel on the agitator during such relative rotation, for adjusting the elevation o f the agitator.

7. A gas producer having an agitator means and a cable transmission system for o erating the same,.the agitator being movabib vertically more or less into the fuel and said transmission syestem having a loop A therein connected to the agitator to control said movement thereof more or less into the fuel.

8. A gas producer having an agitator 'adapted' to operate on the fuel and a cable transmission system for driving the agitator with a rotary movement and having a bight or loop to accommodate endwise movement o-f the agitator and a take-up device for the cable.

9. A gas producer having a rotary affitator, a driving cable, a sheave having splined connection with theagitator and driven by the cable and the cable having a b-ight or loop therein connected to the agitator to accommodate endwise movement of the same.

10. A gas producer having a rotary agitator, a driving sheave in splined connection with the agitator, the driving cable fastened over the sheave, the cable having a loop or bight in connection with the agitator independently of the said sheave and a tension means for the driving-cable whereby the agitator is revolvably driven through the cable and is yet free for endwise movement to adjust the agitator to the Varying height of the fuel in the producer. f

11. A gas producer having a rotary agitator adapted to move vertically to accommodate itself to the level of the vcoal and a driving means for rotating the agitator including a sheave having splined connection therewith.

12. A gas producer having a rotary agitator movable vertically toaccommodate itself to the varying height of the fuel in the producer and a common means for driving and vertically moving the agitator controlled by the torque producer on. the agitator by the fuel.

13. A gas producer having a rotary agitator capable ofvertical movement to accommodate itself to the varying height of fuel a-nd a cable drive system for operating the agitator, such system having a loop or bight in connection with the agitator to bring about the said vertical movement thereof.`

14. A gas producer having an agitator adapted to have horizontally rotary and vertically reciprocating motion, a cable drive system with a tension device therein, a cable having two bights thereinone of which embracesl the rotary motion to the agitator and the other of which is connected to the agitator to control the `said vertical motion therein.J v

15. A gas producer having a fuel feeding chute, a fuel agitating device having an upwiardly .extending :vertically adjustable stem projecting into said chute, an annular bearing for said stem disposed in the path of fuel falling through said chute, said bearing having its upper surface shaped to provide an annular deiecting surface adapted to deflect fuel to the outer annular area of the fuel bed.

16. A gas producer with a fuel agitator adjustable in height and arranged to automat-ically release its driving mechanism agitator and meansfto automatically disconnect its driving mechanism when the height of the fuel exceeds the predetermined point.

18. In Icombination` a producer side wall and a fuel agitator`v mechanism for rotating one relative to the other, said agitator being provided with a singlc upwardly extending leg` and means engaging said leg for Controlling thc elevation of the agitator by the amount of torsional resistance to such relative rotation produced upon the agitator by the fuel.

19. In combination, a fuel agitator having an upwardly extending leg, means for engaging said leg for rotating the agitator, and means whereby the elevation of the agitator is controlled by the horizontal twisting moment produced upon the agitator by the fuel during rotation of such agitator.

20. In a gas producer, an upwardly and downwardly movable agitator, means for causing relative rotation between said agiy tator and the fuel bed, a tension member connected to said agitator, and means for exerting more or less tension upon said member to raise or lower said agitator according to the torsional force produced upon the agitator by such relative rotation.

n testimony whereof I have hereunto signed my name in the presence of two witnesses.

WILLIAM B. CHAPMAN.

Witnesses:

PATRICK A. BOLGER, sAAo B. OWENS. 

